1. Field of the Invention
The present invention relates to terminal devices, such as e-nail terminals and portable information terminals, connected via a network in a document information communication system.
2. Description of the Related Art
In recent years, there has been a rapid increase in the use of a variety of communication devices such as telephones, facsimiles, digital mobile telephones, PHS (personal handy phone system), portable communication terminals, pagers capable of receiving a message and workstations connected to LAN (Local Area Network) and WAN (Wide Area Network). This situation provides users with many opportunities to handle different types of communication terminal devices.
Therefore, there is increasing demand for improved capability of transmitting and receiving a multimedia document which includes data of different media attributes, such as audio data, character data, still image data, motion picture data and hand-written data. However, such communication terminal devices are not readily available to users due to their high cost and bulky size.
A protocol called MIME (Multipurpose Internet Mail Extension) has been established for transmitting such multimedia document in data communication. According to MIME, a plurality of document elements constitute a document, each having a single media attribute and meaning. Each document element has data showing its media attribute and display method.
MIME is described in detail in "Network Working Group Request for Comments 1341".
Generally, a communication terminal device for transmitting a document including different media attributes has a document described in MIME and transmits it to a receiver terminal device. The receiver terminal device decodes the document elements included in the document based on their media attribute data. When the document includes data of a media attribute which cannot be decoded and displayed (outputted), this data is ignored by the receiver terminal device.
FIG. 1 shows the construction of the terminal device in the conventional document information communication system. Transmitter terminal device 11 and receiver terminal device 12 are connected via network 13. Transmitter terminal device 11 comprises document information storage unit 14 and transmission unit 15. Receiver terminal device 12 comprises reception unit 16 and document output unit 17.
Document 20 in FIG. 2 is transmitted from terminal device 11 to terminal device 12 as follows. Document 20 comprises document elements 21, 22, 23, 24 and 25 having "character" as their media attributes and document element 26 having "monochrome still picture" as its media attribute.
Document information storage unit 14 stores document 20 in the form of document information control table 30 shown in FIG. 3. Document information control table 30 comprises element data 31, element data size 32 and media attribute 33. For example, in the case of document element 21 "Notice of a Meeting", its media attribute is "character" and data size is "19". In the case of document element 26, its media attribute is "monochrome still picture" and data size is "1000".
Transmission unit 15 receives a user's indication of a transmission destination terminal (which can be any of the terminals) and document information, reads document information control table 30 stored in document information storage unit 14 and transmits it to reception unit 16 of terminal device 12 via network 13.
Reception unit 16 of terminal device 12 receives document information control table 30 transmitted from terminal device 11. Document output unit 17 decodes information control table 30 and outputs it to the display screen. If terminal device 12 has the same function (output capability) as terminal device 11, document output unit 17 outputs the same document as document 20 shown in FIG. 2 to the display screen. However, if terminal device 12 is a character e-mail terminal which is capable of decoding only element data having "character" as its media attribute, the terminal device outputs only element data of document elements 21, 22, . . . , 25 to the display screen, as is shown in FIG. 4.
As the character e-mail terminal is not capable of decoding and displaying (outputting) the element data of document element 26, the reception of this document 26 is futile.
As mentioned above, it was often likely that such futile communication is often performed by the conventional document information communication system, as transmitter terminal device 11 transmits all of the information in document information control table 30 stored in document information storage unit 14 regardless of the output capability of receiver terminal device 12.
In addition to this problem, it has also not been possible to transmit all of document 20 to receiver terminal device 12.
It can be the case that the intended receiver of the data is in possession of another communication device, aside from receiver terminal 12, which is capable of outputting a different part of the document data. However, in this case, it is still impossible to avoid the futile transmission of data which cannot be outputted to both devices.
Receiver terminal device 12 is indicated by the user in transmission terminal device 11. If the user of receiver terminal device 12 possesses another terminal device, it may be more convenient to transmit the element data to that terminal device.